This invention relates to a process for increasing the concentration of aromatics in a hydrocarbon feedstock which contains paraffins by converting or dehydrocyclizing the paraffins into aromatic compounds. It is particularly concerned with a catalytic process carried out at relatively low temperatures in which the catalyst contains nickel and/or cobalt components but no tungsten or other Group VIB metal components and the feedstock boils in the diesel range.
Relatively high molecular weight aromatic compounds, such as those containing 12 or more carbon atoms, are in high demand in the petrochemical industry for use as solvents or as high valued intermediates in the formation of many different types of products including plastics and fabric dyes. As an example, naphthalene is a highly desired intermediate for making phthalic anhydride, naphthol, naphthol derivatives and dyes and finds direct use as a solvent. Anthracene is used directly in making dyes and in printing applications.
The major source of aromatic compounds for use in the petrochemical industry is the catalytic reforming of gasoline or other naphtha boiling range hydrocarbons. Unfortunately, the catalytic reforming of gasoline to make aromatic compounds has two major drawbacks. First, it decreases the amount of lower boiling hydrocarbons available for use as gasoline, which is in high demand as a fuel, and secondly, it results primarily in the production of lower molecular weight aromatics such as benzene, toluene and xylene. Although higher molecular weight aromatics such as naphthalene and anthracene can be derived from coal tar, the use of this source of aromatics is steadily declining. Thus, there exists a current need for the production of aromatic compounds from sources other than gasoline, naphtha, and coal tars via a process which has high selectivities for aromatics, particularly higher molecular weight aromatics containing 12 or more carbon atoms.